1 Technical Field
This disclosure relates generally to an engine starting apparatus equipped with an engine firing-up detector which works to detect the fact that an engine has been fired up.
2 Background Art
There is known a technique of using a value of the speed of an engine or electric current in an electric motor installed in an engine starter as a reference value for determining whether the engine has been started by the engine starter and fired up or not. Specifically, such a system is, as illustrated in FIG. 4, designed to determine that the engine has been fired up (a) when the speed of the engine reaches a given value (e.g., 600 rpm) and (b) when the value of electric current in the engine starter has dropped to a value (i.e., about a no-load current) smaller than a variable range of current consumed by the engine starter in cranking the engine. For example, Japanese Patent Application No. 4108920 teaches the above type of system.
Pinion kick starters designed to kick out a pinion gear into mesh with a ring gear to start the engine usually generate tooth hammering noise between the pinion and the ring gear which arises from a variation in torque during cranking of the engine. In the case of use of such pinion kick starters in automotive vehicles equipped with an idle-stop system (also called an automatic engine stop and restart system), the tooth hammering noise will occur when the engine is restarted, which gives vehicle operators an uncomfortable feeling. In order to alleviate this problem, it is necessary to de-energize the starter as soon as possible after the engine is fired up to move the pinion out of engagement with the ring gear.
Shortening the time needed to restart the engine requires increasing the speed at which the starter cranks the engine to as high as possible.
Use of high speed starters to reduce the time required to restart the engine, however, encounters a difficulty in accurately determining the firing up of the engine by means of the above conditions (a) and (b). The high speed starters, as referred to herein, are starters which are capable of making the circumferential speed of the pinion continue to follow that of the ring gear of the engine at least until start of the third compression stoke of the engine after the engine completes the second compression stroke or in which the speed of cracking the engine will exceed 600 rmp. “The circumferential speed of the pinion continues to follow that of the ring gear” means that torque, as produced by an electric motor of the starter, continues to be exerted by the pinion on the ring gear during cranking of the engine, for example, at least until the start of the third compression stroke of the engine.
The use of the above high speed starters may cause the cranking speed to reach an engine speed which may be used as a reference value at which typical engines are determined as having been fired up. It is, therefore, difficult to determine whether the fact that the reference value is reached results from the firing up of the engine or is caused by the aid of rotation from the starter not the firing up of the engine.
The no-load speed of typical starters usually increases up to a maximum of 350 rpm to 450 rpm, while the no-load speed of the high speed starters increases up to as high as an idle speed of the engine, thus causing the current flowing in the starter motor after the engine is fired up to have a varying waveform similar to that appearing during the cranking of the engine without converging on a constant level. It is, therefore, impossible to determine the firing-up of the engine accurately based on the above condition (b) using the value of current in the starter motor.